1. Field of the Invention
The present invention relates to an improvement of a blower for use in various kinds of office automation apparatus, in particular, an improvement on thin type blower.
2. The Related Art
In an apparatus like an office automation apparatus which accommodates various kinds of electronic parts within a casing, heat generated by such electronic parts remains inside the casing which may cause the electronic parts to be broken. Therefore, the side wall of the casing is provided with a vent, in which a blower is mounted to discharge the heat in the case outside. The blower thus used has often been provided with two ball bearings in order to prevent the vibrations in both axial and radial directions to make the blower rotate stably.
Recently, the office automation apparatus has been developed to make it miniaturized. As the miniaturization develops, the blower itself is requested to be miniaturized in size and thickness. When the miniaturization in size and thickness is realized, a high precision bearing has to be used, since the allowable vibration of the rotary shaft supported by the bearings becomes narrower.
When high precision bearings are used to prevent vibration of a rotary shaft, it is often practiced to juxtapose two bearings (ball bearings) in a cylindrical bearing box. When juxtaposing two bearings, the vibration becomes small since the supporting span becomes large. However, when the supporting span is made long as described, the coaxiality of the two bearings has to be kept at a small rate, since otherwise a tension from an undesirable direction will effect the rotary shaft. It has been found that in general, the coaxiality of the two bearings to be used in a blower for office automation apparatus has to be kept at 0.01 mm or less.
As a result, the coaxiality between the two bearings will be kept at a rate of 0.01 mm or less, however achieving this precision while inserting two bearings into a resin-made bearing box requires a high level of technique and is not feasible easily.
The present invention has been made in the light of this problem, and with a comparatively easy structure it is intended to provide a blower, in which its coaxiality of used bearings is made to be kept at 0.01 mm or less.
The present invention has been made to solve the above problem and according to a first aspect of the present invention, an impeller is fixed on one end of a shaft rotatably supported by bearings, where a ring-like magnet is provided inside the said impeller; characterized that on a blower causing said impeller and said shaft to rotate by the effect of a magnetic interference with the aforementioned magnet by supplying a current on a winding provided at a location relative to the said magnet of the stator, 2 ball bearings on which the width of the inner ring is smaller than the width of the outer ring, inserted into a bearing housing from one side, are used as aforementioned bearings.
Further, according to a second aspect of the present invention, an impeller is fixed on the end of a shaft rotatably supported by bearings, where a ring-like magnet is provided inside the said impeller; characterized that on a blower causing said impeller and said shaft to rotate by the magnet by supplying a current on a winding provided at a location relative to the said magnet of the stator, that 2 bearings, on which inner ring width is larger than the outer ring width are inserted into a bearing housing from one side, one of the inner race of the 2 bearings is pushed towards the outer bearing by a spring, are used as aforementioned bearings.
By the construction of the first aspect, since the width dimension of the inner race inserted in the resin-made bearing box from one side thereof is smaller than the width of the outer race, if the outer race is contacted, the inner race is not, the two bearings become possible to be turned within a minute area at the contacting point as the turning center. Due to this turning, since the outer race and inner race can be displaced to the shaft, those are fixed at a position where the coaxiality is minimum.
Further, if constituted according to the second aspect, since one inner race of the two bearings is pushed toward the other bearing by a spring and a pressurization is given, it becomes possible to maintain the position where the coaxiality becomes minimum.